dm snapshot: add new persistent store option to support overflow
Commit 76c44f6d80 introduced the possibly for "Overflow" to be reported
by the snapshot device's status. Older userspace (e.g. lvm2) does not
handle the "Overflow" status response.
Fix this incompatibility by requiring newer userspace code, that can
cope with "Overflow", request the persistent store with overflow support
by using "PO" (Persistent with Overflow) for the snapshot store type.
Reported-by: Zdenek Kabelac <zkabelac@redhat.com>
Fixes: 76c44f6d80 ("dm snapshot: don't invalidate on-disk image on snapshot write overflow")
Reviewed-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
diff --git a/drivers/md/dm-exception-store.c b/drivers/md/dm-exception-store.c
index ebaa4f8..192bb8b 100644
--- a/drivers/md/dm-exception-store.c
+++ b/drivers/md/dm-exception-store.c
@@ -203,7 +203,7 @@
return -EINVAL;
}
- tmp_store = kmalloc(sizeof(*tmp_store), GFP_KERNEL);
+ tmp_store = kzalloc(sizeof(*tmp_store), GFP_KERNEL);
if (!tmp_store) {
ti->error = "Exception store allocation failed";
return -ENOMEM;
@@ -215,7 +215,7 @@
else if (persistent == 'N')
type = get_type("N");
else {
- ti->error = "Persistent flag is not P or N";
+ ti->error = "Exception store type is not P or N";
r = -EINVAL;
goto bad_type;
}
@@ -233,7 +233,7 @@
if (r)
goto bad;
- r = type->ctr(tmp_store, 0, NULL);
+ r = type->ctr(tmp_store, (strlen(argv[0]) > 1 ? &argv[0][1] : NULL));
if (r) {
ti->error = "Exception store type constructor failed";
goto bad;
diff --git a/drivers/md/dm-exception-store.h b/drivers/md/dm-exception-store.h
index 0b25362..fae34e7 100644
--- a/drivers/md/dm-exception-store.h
+++ b/drivers/md/dm-exception-store.h
@@ -42,8 +42,7 @@
const char *name;
struct module *module;
- int (*ctr) (struct dm_exception_store *store,
- unsigned argc, char **argv);
+ int (*ctr) (struct dm_exception_store *store, char *options);
/*
* Destroys this object when you've finished with it.
@@ -123,6 +122,8 @@
unsigned chunk_shift;
void *context;
+
+ bool userspace_supports_overflow;
};
/*
diff --git a/drivers/md/dm-snap-persistent.c b/drivers/md/dm-snap-persistent.c
index bf71583..aeacad9 100644
--- a/drivers/md/dm-snap-persistent.c
+++ b/drivers/md/dm-snap-persistent.c
@@ -7,6 +7,7 @@
#include "dm-exception-store.h"
+#include <linux/ctype.h>
#include <linux/mm.h>
#include <linux/pagemap.h>
#include <linux/vmalloc.h>
@@ -843,8 +844,7 @@
DMWARN("write header failed");
}
-static int persistent_ctr(struct dm_exception_store *store,
- unsigned argc, char **argv)
+static int persistent_ctr(struct dm_exception_store *store, char *options)
{
struct pstore *ps;
@@ -873,6 +873,16 @@
return -ENOMEM;
}
+ if (options) {
+ char overflow = toupper(options[0]);
+ if (overflow == 'O')
+ store->userspace_supports_overflow = true;
+ else {
+ DMERR("Unsupported persistent store option: %s", options);
+ return -EINVAL;
+ }
+ }
+
store->context = ps;
return 0;
@@ -888,7 +898,8 @@
case STATUSTYPE_INFO:
break;
case STATUSTYPE_TABLE:
- DMEMIT(" P %llu", (unsigned long long)store->chunk_size);
+ DMEMIT(" %s %llu", store->userspace_supports_overflow ? "PO" : "P",
+ (unsigned long long)store->chunk_size);
}
return sz;
diff --git a/drivers/md/dm-snap-transient.c b/drivers/md/dm-snap-transient.c
index 1ce9a25..9b7c8c8 100644
--- a/drivers/md/dm-snap-transient.c
+++ b/drivers/md/dm-snap-transient.c
@@ -70,8 +70,7 @@
*metadata_sectors = 0;
}
-static int transient_ctr(struct dm_exception_store *store,
- unsigned argc, char **argv)
+static int transient_ctr(struct dm_exception_store *store, char *options)
{
struct transient_c *tc;
diff --git a/drivers/md/dm-snap.c b/drivers/md/dm-snap.c
index c0bcd65..c06b74e 100644
--- a/drivers/md/dm-snap.c
+++ b/drivers/md/dm-snap.c
@@ -1098,7 +1098,7 @@
}
/*
- * Construct a snapshot mapping: <origin_dev> <COW-dev> <p/n> <chunk-size>
+ * Construct a snapshot mapping: <origin_dev> <COW-dev> <p|po|n> <chunk-size>
*/
static int snapshot_ctr(struct dm_target *ti, unsigned int argc, char **argv)
{
@@ -1302,6 +1302,7 @@
u.store_swap = snap_dest->store;
snap_dest->store = snap_src->store;
+ snap_dest->store->userspace_supports_overflow = u.store_swap->userspace_supports_overflow;
snap_src->store = u.store_swap;
snap_dest->store->snap = snap_dest;
@@ -1739,8 +1740,11 @@
pe = __find_pending_exception(s, pe, chunk);
if (!pe) {
- s->snapshot_overflowed = 1;
- DMERR("Snapshot overflowed: Unable to allocate exception.");
+ if (s->store->userspace_supports_overflow) {
+ s->snapshot_overflowed = 1;
+ DMERR("Snapshot overflowed: Unable to allocate exception.");
+ } else
+ __invalidate_snapshot(s, -ENOMEM);
r = -EIO;
goto out_unlock;
}
@@ -2365,7 +2369,7 @@
static struct target_type snapshot_target = {
.name = "snapshot",
- .version = {1, 14, 0},
+ .version = {1, 15, 0},
.module = THIS_MODULE,
.ctr = snapshot_ctr,
.dtr = snapshot_dtr,
@@ -2379,7 +2383,7 @@
static struct target_type merge_target = {
.name = dm_snapshot_merge_target_name,
- .version = {1, 3, 0},
+ .version = {1, 4, 0},
.module = THIS_MODULE,
.ctr = snapshot_ctr,
.dtr = snapshot_dtr,